Why not the Lightweight Storm in .223? Have you looked into a simple re-barrel of the gun you have? I have a 110 Storm ( not the Lightweight model ) in .223 and it`s been great.
Doesn't look like I can edit the original post to clarify, but by "landed on" I only mean decided, not purchased. Fortunately I had enough smarts to post the plan here for critique before sending money anywhere.
Re: recoil & weight
ResearchinStuff's mentioning of how .223 recoil is shaking his 75lb kid is a damn good data point for me. My daughter is light for her age and looks to be staying that way, so I think using .223 as a benchmark for total recoil is a good idea. I think this keeps Grendel on the table (for now) because of how similar their recoil is, particularly tamed with a suppressor, but this dovetails into the discussion about progression as they grow in size and experience. It's looking more and more like a .223 rifle is both a good starting point for the kids and good enough on local (FL) game for me to practice on.
My kids are both still quite young and small. My youngest (son) hasn't really expressed any special interest in shooting, but my daughter is all of 50lbs and is now officially tall enough to ride all of the roller coasters. Dainty thing but in the midst of a growth spurt as we speak. She and mama love my little M&P 15-22, but my offspring specifically wants to come out with her old man to hunt. It's probably the most adamant she's ever been about showing interest in something so I want to develop this as much as possible.
Re: learning cost
My stockpile of .223 and 5.56 is primarily oriented towards work and training with ARs; a couple cases of Wolf Gold, a few hundred rounds of this Australian-made .223 w/ 69gr smk that's silly accurate out of every gun I've seen it shot through, and the Gold Dots from work. Whatever gun and caliber I get, I'll have to get ammo for. I expect this and it's part of the planning process.
Rifle Ergos
Aside from being reasonably priced, the only hard stipulation I have about the rifle suggestions is that they either come with a stock that has a more vertical grip or a lighter weight (<3lb) stock/chassis is available for it that has a more vertical grip. I've got some pretty poor wrist flexibility and the more traditional grip angles range from very uncomfortable to painful for me. For my original plan, I had expected to replace the Savage stock with a Mesa Precision Altitude at some point; a stock like this one checks basically all of the boxes for me.
I'm still reading through PNWGATOR's topic on hunting with the .223, but it's confirming my suspicion that much of my "knowledge" from the more tactical LEO space is at pretty stark odds with the experiences of hunters. More and more it appears that, like with handguns, shot placement (marksmanship) and a good bullet design are much bigger factors than the actual cartridge for successful hunts. This is something I'm going to need to mull over more because it's such a different thought process than I've had prior to deciding I wanted to get into hunting.